SIRPα and FcγRI nanoclusters are constitutively associated in nonactivated human macrophages but segregate upon activation with hIgG. (A) TIRF and dSTORM images showing FcγRI (green) and SIRPα (red) at the surface of human macrophages incubated for 10 min on slides coated with PLL (nonactivated, top) or hIgG (middle) and stained with anti–FcγRI-AF488 and anti–SIRPα-AF647 mAbs. Bars, 5 µm. Regions outlined by the white squares (middle column) are shown enlarged (right columns) with relative fluorescence intensity profiles along the white lines. Bars, 1 µm. As a positive control, macrophages seeded onto PLL-coated slides were stained with anti–FcγRI-AF488 mAb followed by anti–mouse IgG1-AF647 secondary antibody (bottom). (B) CBC histograms of the single-molecule distributions of the colocalization parameter for SIRPα and FcγRI in cells seeded onto PLL- (gray) or hIgG-coated (red) slides for 10 min or for positive control data (green). Data are from a minimum of 30 cells from three independent donors. Bars represent mean ± SD. (C) Nearest-neighbor (NN) analysis from data shown in (B). Each symbol represents the median NN of all paired single-molecule localizations from one cell. Horizontal lines and error bars represent mean ± SD. ****, P < 0.0001; two-tailed t test assuming unequal variance. (D) Histogram distributions of the NND between the centroids of nanoclusters from one channel and the centroid of their nearest neighbor from the second channel (≥ 20,000 clusters from a minimum of 10 cells per condition) from cells seeded onto PLL- (light gray), hIgG-coated (light red) slides, or positive control data (green). Corresponding simulated data are also shown, in which the centroid positions of SIRPα nanoclusters in both nonactivating (dark gray) and hIgG-activating conditions (dark red) were randomized within the cell area.

SIRPα and the low-affinity Fc receptor, FcγRII, are segregated on a nanometer scale. (A) TIRF and dSTORM images showing FcγRII (green) and SIRPα (red) at the surface of human macrophages incubated for 10 or 30 min on slides coated with PLL (nonactivated) or hIgG and stained with anti–FcγRII-AF488 and anti–SIRPα-AF647 mAbs. Bars, 5 µm. In each condition, regions outlined by the white squares (middle column) are shown enlarged (right column) with relative fluorescence intensity profiles along the white lines. Bars, 1 µm. (B) CBC histograms of the single-molecule distributions of the colocalization parameter for SIRPα and FcγRII in cells seeded onto PLL- or hIgG-coated slides for 10 (light gray and dark gray, respectively) or 30 min (light red and dark red, respectively) or for positive control data (green). The positive control data in this figure is the same as in Fig. 2. Data are from a minimum of 30 cells from three independent donors. Bars represent mean ± SD. (C) NND analysis from data shown in B. Each symbol represents the median NND of all paired single-molecule localizations from one cell. Horizontal lines and error bars represent mean ± SD. ns, not significant; **, P < 0.01; ***, P < 0.001; one-way analysis of variance (ANOVA) with Tukey’s post-hoc test. (D) Histogram distributions of the NND between the centroids of nanoclusters from one channel and the centroid of their nearest neighbor from the second channel (≥20,000 clusters from a minimum of 10 cells per condition). a.u. arbitrary units; NN, nearest neighbor; PC, positive control.

FcγRs reorganize into concentric rings upon activation. (A) TIRF images of FcγRI (top) and FcγRII (bottom) at the surface of human macrophages incubated for 10 or 30 min on slides coated with PLL (nonactivated) or hIgG and stained with fluorescently labeled specific antibodies. Bars, 10 µm. (B) TIRF and dSTORM images of FcγRI (green) and FcγRII (red) at the surface of macrophages incubated for 10 or 30 min on slides coated with PLL or hIgG and stained with anti–FcγRI-AF488 and anti–FcγRII-AF647 mAbs. Bars, 5 µm. Regions outlined by the white squares (middle column) are shown enlarged (right column) with relative fluorescence intensity profiles along the white lines. Bars, 1 µm. (C) CBC histograms of the single-molecule distributions of the colocalization parameter for FcγRI and FcγRII in cells seeded onto PLL- or hIgG-coated slides for 10 (light gray and dark gray, respectively) or 30 min (light red and dark red, respectively) or for positive control data (green). The positive control data in this figure are the same as in Fig. 2. Data are from a minimum of 10 cells from three independent donors. Bars represent mean ± SD. (D) NND analysis from data shown in C. Each symbol represents the median NND of all paired single-molecule localizations from one cell. Horizontal lines and error bars represent mean ± SD. ns, not significant; **, P < 0.01; ****, P < 0.0001; one-way ANOVA with Tukey’s post-hoc test. (E) Histogram distributions of the NND between the centroids of nanoclusters from one channel and the centroid of their nearest neighbor from the second channel (≥20,000 clusters from a minimum of 10 cells per condition). a.u., arbitrary units; NN, nearest neighbor; PC, positive control.

Rearrangement of macrophage surface receptors triggered by mobile hIgG. (A) TIRF images of FcγRI at the surface of human macrophages incubated for 10 min on SLBs loaded with streptavidin (nonactivating) or with streptavidin-hIgG (activating) and stained with a fluorescently labeled specific antibody. Two example images are shown for each condition. Bars, 10 µm. (B) dSTORM images of FcγRI (green) and SIRPα (red) at the surface of macrophages seeded as in A and stained with anti–FcγRI-AF488 and anti–SIRPα-AF647 mAbs. Bars, 5 µm. Regions outlined by the white squares are shown enlarged with relative fluorescence intensity profiles along the white lines. Bars, 1 µm. (C–E) Nanocluster areas (C), density (D), and percentage of localizations in nanoclusters (E) for SIRPα and FcγRI under nonactivating (black) or hIgG-activating (gray) conditions. Each symbol represents the median of several 5 × 5 µm regions from the same cell. Horizontal lines and error bars represent mean ± SD. Data are from a minimum of 30 cells from two independent experiments. ns, not significant; *, P < 0.05; ****, P < 0.0001; two-tailed t test assuming unequal variance. (F) CBC histograms of the single-molecule distributions of the colocalization parameter for SIRPα and FcγRI in cells seeded as in A. Data are from a minimum of 30 cells from two independent experiments. Bars represent mean ± SD. (G) NND analysis from data shown in F. Each symbol represents median NND of all paired single-molecule localizations from one cell. Horizontal lines and error bars represent mean ± SD. ****, P < 0.0001; two-tailed t test assuming unequal variance. (H) Histogram distributions of the NND between the centroids of nanoclusters from one channel and the centroid of their nearest neighbor from the second channel (≥10,000 clusters from a minimum of 10 cells per condition) from cells seeded onto control nonactivating (light gray) or hIgG-loaded activating (light red) SLBs.